Over the last decade, minimally invasive surgical techniques have gained wide use and great popularity. Such techniques generally involve a combination of miniaturized cutting tools in concert with remote viewing devices that can be inserted through small incisions and delivered to a site well inside the body cavity to carry out desired surgery. Such techniques are advantageous over standard invasive surgery in that patient trauma is minimized and recovery time is markedly shortened.
One of the most popular applications of minimally invasive surgery is in the area of arthroscopic surgery. Such surgery allows joints to be repaired without having to cut through or open up healthy areas of the joint to be treated. However, operating within a joint is limited by the space available among and between the joint tissues and ligaments for maneuvering cutting devices.
In response to space limitations imposed on cutting devices to be used within joints and similarly constrained spaces, cutters relying on the shearing forces created by the interaction of at least two separate cutting surfaces have been proposed. U.S. Pat. No. 4,203,444 to Bonnell et al. discloses one such device. The Bonnell device utilizes an outer tube having a side-facing, axially extending cutting port and an internal rotary blade. A vacuum conduit draws the tissue to be sheared into the cutting port while the rotary blade is driven in shearing relation to the external tube. The vacuum further draws the cut body tissue through a tube lateral to the handle and out of a side port of the instrument for disposal.
U.S. Pat. No. 4,601,290 to Effron et al. discloses another example of a shearing cutter. The Effron device utilizes an outer tube having both a side-facing and end facing cutting port with a cutting edge and an internal tube having an internal opening having cutting edges thereon. The external and internal openings and edges are relatively moveable to open to receive the body tissue there through and to close in order to cut body tissue. A vacuum means into the external and internal openings where the tissue is sheared by the combined cutting forces of the internal and external tubes. The cut tissue is then drawn through the inner tube and subsequently out of the cutting device for disposal.
Unfortunately, existing cutting devices, such as those described above, exhibit serious problems that impair their usefulness in arthroscopic and other minimally invasive surgical applications. Some devices, such as the Bonnell instrument, are given to spooling or clogging when cutting through soft fibrous tissue. Further, rapid blade dulling, particularly when cutting very hard tissue such as cartilage or bone, often occurs significantly impairing the instrument's ability to cut hard tissues.
Another major disadvantage encountered with known surgical devices of this type stems from the cylindrical configuration of the rotating cutting edges. Much like the action of a mellon-bailer, tissue removal creates a depression with a curved, concave surface, as opposed to a box-like depression with more or less flattened sides. As much as the surgeon may attempt to match the equator of the concavity, removal of additional tissue always leaves behind a ridge or protrusion on the treated surface. Such protrusions are particularly disadvantageous in joint surgery where jagged or protruding surfaces on cartilage or bone can inhibit free joint movement and lead to pain and inflammation after surgery.
A further problem encountered is that of aspiration. Many existing cutting devices fail to aspirate the treatment area during surgery. Others employ a somewhat bulky and awkward side tube that is connected directly to the cutter rather than passing through the handle of the device.
In view of the foregoing, there is a need for a compact surgical cutting device for use in restricted spaces, the dimensions of which remain more or less constant during operation but that does not clog or spool during use and that effects prompt removal of tissue from the treatment site as the tissue is cut away by the cutting device. There is also a need for a surgical cutting device that leaves behind a surface that is more or less normal in topography for the joint or region being treated after desired tissue is removed, thereby avoiding the production of ridges, protuberances or odd shaping that may hinder or make painful joint movement after surgery. There is a further need for a surgical cutting device that permits more efficient cutting and sculpting of medium to hard body tissue in order to reduce the duration of surgery.
There is also a need for a surgical cutting device that allows soft tissue to be removed at selected times which at other times during an operation will act only on medium to hard tissue.